This invention relates to accelerometers, and in particular, to a device which utilizes the principles of mass-loaded cantilever beam accelerometers
Many micromechanical sensing devices are now well known. Such devices include sensors of all types, for example, for sensing force, pressure, acceleration, etc. These devices are termed "micromechanical" because of their small dimensions - on the order of a few centimeters square or smaller. The small size is generally achieved by employing photolithographic technology similar to that employed in the fabrication of printed circuits. With this technology, the devices are as small as microelectronic circuits, and many such devices are often fabricated in a batch on a single substrate, thereby spreading the cost of processing that substrate among many individual devices. The resulting low unit cost increases the applications for such devices.
Prior art micromechanical acceleration sensors have suffered from a number of disadvantages which have raised their cost of manufacture, limited their accuracy, and precluded their use in many applications. For example, for greater sensitivity to small acceleration forces, the cantilever beam suspending the mass must be more flexible and must work across an exceedingly small gap. Slight distortions of the beams result in proportionally large changes in the tiny gap used to establish acceleration threshold. The manufacturing, alignment and adjustment steps required to achieve high precision and reliability add cost to the product while reducing yield.